Damping unit for watt-hour meters



Patented Mar. 8, 1949 DAMPING UNIT FOR WATT-HOUR BIETERS Stanley S. Green, La Fayette, Ind., assignor to Duncan Electric Manufacturing Company, La Fayette, Ind., a corporation of Illinois Application December 2, 1944, Seria-l No. 566,295

2 Claims. l

In my Patent No. 2,110,418, I disclosed the use of high coercive magnetic metal, such as Alnico, in the damping magnets of watt-hour meters. One of the important advantages of this metal for this use is in its resistance to weakening by stray magnetic fields such as those encountered due to unusual surges of current caused by lightning or short circuit.

In this matter of withstanding stray elds, the invention represented by that application comprised a tremendous forward step. As compared to the prior conventional damping units, the Alnico damping unit seemed substantially immune to weakening even -by lightning surges. As a result of that advance, the standards of the meter industry have been raised to such an extent that there is now some demand for still further stray eld resistance. According to the present invention, the immunity of the damping unit is still further increased. For the purpose of illustration, it might be said that the present invention represents almost as much of an advance as did the last in the sense of the percentage of the remaining distance towards perfection which the invention bridges.

Even aside from the desire to obtain greater immunity, there has been a desire to provide other simple ways of using Alnico and like metals and preferably ways that are even simpler at least from the standpoint of permitting the use of simpler shapes of Alnico. Alnico is difficult to machine. The U-shaped magnet of my prior patent constituted one way of using a minimum of machining. According to the present invention, this same minimum of machining of the Alnico is attained with a simpler shape. One of the difficulties in obtaining simplicity without machining has been the difculty of securing the Alnico in place. According to the present invention, this diculty is solved by the simple expedient of pressing a simple block of Alnico of rounded cross-section, such as a cylinder, into a tight-fitting sleeve of non-magnetic metal which is provided with securing lugs through which screws may be passed. This non-magnetic sleeve is preferably copper so as to form a shield against the stray alternating elds such as those produced by lightning surges.

Probably the most eilicient way to use the flux available from a single cylinder is to divide the flux into two paths so that after passing up through the disk, the two paths will separate and pass downwardly through the disk on opposite sides of the upward flux. This is accomplished by the very simple expedient of securing the ensleeved Alnico to a U-shaped magnetic yoke which forms the two returned paths, a simple armature being, of course, positioned on the opposite side of the disk. This combination of the magnetic yoke and armature again serves to shield the magnet from surge effects in spite of the fact that it forms the magnetic gaps through which the disk rotates. Thus without any parts that are not otherwise useful, triple protection against stray surge effects is provided producing van eX- tremely high degree of immunity. The three eiects are the inherent resistance to weakening of the Alnico or other high coercive metal, the eddy current type of shielding provided by the securing sleeve and the by-passing or shunting type of protection provided by the yoke and armature in spite of the magnetic gaps therein.

Additional objects and advantages will become apparent as the disclosure proceeds and the description is read in conjunction with the accompanying drawings, in which Fig. 1 is a diagrammatic face View of the meter mechanism chosen for illustration of the invention;

Fig. 2 is a fragmentary view of the structure of Fig. 1 with certain parts removed to expose the damping unit;

Fig. 3 is a fragmentary, vertical, sectional view taken approximately on the line 3 3 of Fig. l;

Fig. 4 and Fig. 5 are, respectively, plan and front elevational views of the magnet unit of a preferred modification of the invention.

Although the law requires a full and exact description of at least one form of the invention, such as that which follows, it is, of course, the purpose of a patent to cover each new inventive concept therein no matter how it may later be disguised by variations in form or additions of further improvements; and the appended claims are intended to accomplish this purpose by particularly pointing out the parts, improvements, or combinations in which the inventive concepts are found.

The illustrated forms of the inwention are shown in conjunction with a watt-hour meter which includes a conventional driving element Il, ya conventional frame i2, a conventional disk I3 rotatably carried by the frame, and the damping unit I Il which lis the subject of the present invention. In both of the illustrated forms of the invention, the damping unit I 4 includes a damping frame i6 which may be secured to the frame l2 or an adapter I1 in any suitable manner. The frame i5 straddles the disk so as to support the magnet unit on one side of the disk and the armature I8 on the other side of the disk.

dition around the cylinder 2I.andis .securedto the yoke 22 by suitable screWs'Zllv The'stretched' condition of the sleeve 23 issobtainedbyf making... it initially of a slightly smallerinternalfdiamee ter than the external diameter of thecmagnetfl.-

and pressing the sleeve overthe magnet, or the magnet into the sleeve with a; suitable' powerv press. The screws 24 may be threaded intoholes in the sleeve 23.

Alternatively; .the sleeve.. 23.may,. be .provided with .lugseop ears .26 "nent'..tlielfefOllfl- Orl Secured thereto..and through. .whichscrews'l'may pass to screw 'into'.the: yoke..2 Zas. seen. inflige,A 4 `and`5l f The yoke.- 2 2e mayy be ,securedltm the frame.; i6 inanyfsuitablomannerfas.byiscrewsl8T..

The..armature, I8 may; be` formed inlone. piece or; forithe.saketoi-.providingsadustability., it may befformedain.threefpieces,.,the central portion .b`ee ing fan adjustable' plugsmovediorwardlyjand rearwardly .Y by,V adjustment .screw 29?.. A .suitableconstruction is` illustrated. in. my. prior. Patenti N. 2,252,483, In .this instance,. however, the plug shuld be considerably widen than .that there illustrated. because.:oi. the di'ffrerentinature .ofl th'e magnet. obtainedi by.. moving.; the.. whole. armatura., the lovverA magneti-unit. including@ the magneti and yoke, or the entiredampingfunit..

Any suitable form ofsgtemperature-compensa' tionfmayabeproifided Forsexample,` one or more strips-i3! of suitablemetal having-,anegativetemperature coe'cient of permeability may extend from one .ende toJ the other. off. the. magnet'.Y Z'l'l These maya-be. securedmy being;I held againstl,the magnet by the sleeves 23'and'if;desired;this;sleve may be.y initiallyf groovedl to.. receive. them,l al1 though@5 the groove shouldlnot.beqllite as thick as.- thel strip, 3l.. By.y making the sleeve 23;` of

slightht larger. internall disimeterA than. it wouldv be without-the. strip 3l; thesgrooyingmay be dis'- pensed `withi.

To obtain a high ldegree. of magneticefciency., itzis desirablethat .themagnetZ'l .be in direct'contact-.with .the yoke. 22,. Thismay` b'e ensured"by havingsthemagfnetlil'project at leastgon'e or`tWo-^ thousandths of, anincli below the sleeve123.

In: addition.. to the advantages ofI simplicity andltripleprotection against' we'akeningny,v stray helcls..described`v above, ,the .forni of. magnet here contemplated will,Y by. somaniodi'cattn, lend"`it self 'to an additionaladvantage; It`has'zlnfgibeen recognized to.be.desirable to be able tdrernov'e the. disk". from the.. meter` without disturbing.; the

dampingunit: The .present"stylefofdampingunit with .the single" magnetandtwo return'paths on opposite' sides thereof rlendsitselto` accomplish; ingf thisresult; This' is lbecauseth'e zone'immediately across the center'cf th'esmagneh crossing in a'. front' to4 rearA directionv` is' relatively 11n-iinportant: The flux fromth'e magnetl 2l ltends'f'to concentrate nearI` the/rsids-fof thelmagnettoward the poles-` 32" of" theyoke2` 225 The centralpor'- tion' ofiy the arma-ture l8'f'can-b'el removed with littleeflect. B'y omittingtli'e centralp'ortionl-of the armatureandproducing af completes. gapi at in a stretched corr-s- Alternatively, .thead'justment 1 ciouldbe portion this point free of other obstructions, a channel is formed for the passage of the shaft 33 of the disk through the damping unit. Of course in this event, the frame IIB should not straddle the disk but instead the armature I8 should be carried directly by the main frame I2. This will leave an unobstructed: passage foratherdiskito be ldrawn out between the. armature andltheamagnetunit. In this event, the lower bearing of the disk, or the thereafter carried by the disk, preferably than slightly below the lower" face' ofthe disk. If necessary, however, the magnet 22;.andzsleeve 23 could be notched topermit-.passageiofthis bearing.

Ofcursesomecfeatures of the invention can beused without.others when for any reason it is not' desirectto take full advantage of the benefitswhicn can be obtained by the preferred form of the invention. For example, one leg of the yoke` could. be omitted, thus. providing an. essentially; C-shapedstructuree. Alsothe-shieldvng.,ad= vantage could; be, obtained .without` using.: the sleeve for. securing., the-.magnet yand.;some-.ofth'e shield-ing..advantagesould be obtained eveniii the.. nonemagnetc. shield;.were..omitted.'.v O'n vthe other.' handtheuse.. of the.. sleevewhichn in stretchedcondition on the magnetron securing th@ magnet .istitselt very..v useful .eyen..if,. none'.- of theother. featuresishown.I aresprovidedj In facti this.. could! be a. very.. useful way. of., securing.. a magneteven .invery dierentapparatus. Other shapes'foffmagnet couldlbe used, .andisomeother simpleshapes, especially blockstorounded.crosse section, .su-cli as `circular.,ovalior rectangulanwith rounded. corners,- arenearly; asadVantageOus-as cylinders. Aslighttaprer towardthe ,exposed .pole mightfbe .benen cial.;

I\ claim:

1...Afdamping: unit.. for wattfhour meters yin! cluding, asmagneti ot; highly retentive magnetic rnetaliin itheirmofflasimple.straightblockhaw ing opposite-ly, facing.E pole yfaces,., a shielding.k and flux-carrying., structure comprising aeplurality of pieces of substantially non-retentive: magnetic metal.. jointly forming.; withrthe--magnet annag-A netio. cir cuitwith .tw-of. aligned diskereceiving-fgaps` therein magnetically: in.- series.. with. each other and, the. magnet, said. piecesa-with said. gaps .jointe 1yl forming;y within. said circuit. an lowereluctance magnetic: pathextendingtfrom onepole-facealate erally away from `themagnet, v lengthwiseof 'the magnete laterallytoward,the..mag-net..and tothe otheri poleff ace, .one of .saidpieces inssaid-circuit befingiincontaet .with oneof .said pole. faces; and a. preformed' body, of.. highly,- electro-conductive metal surrounding said magnet. substantially from. voneepole.' face to ithe. other.. and .additionally serv-ing to lhold saidnnagnetin. position..

2. A-,dampirigunitl-for wattehour metersine cludinglfa magnett of highly rete-ntive. magnetic metal .-in'.the.form.of .asi-mpleastraghtiblockihaw ing-'1,oppositelyyfacing; pole faces, a-shieidingfga and iuxecamrying structure comprising; a.- plurality, oi pieces-i of." substantially." nonf-retentivek. magnetic metaly jointlyl forming with:themagnettapainof magneticfcircuitsswithitlieemagnetzlassaecommon element and with atlleast three:alignedrdi-skfrev cetvinggans? thereinr oi;` which: gaps two. arel in each. circuitiv magnetically@ in; series.- with: each otherrandstheernagnet; and said: pieces with said diskqreceivingt gapsi. jointly forming;I withinI each ofi said` circuits.i a low reluctance:r magnetic path extendingeifrom:one'polerfazeeelaterallyyaway from the magnet; lengthwisec of:y the; magnetslaterally toward-.x the f magneti; and:I to.. the other-r yp lef': face;

will not.. extend more REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Number Name Date Burton July 30, 1940 Holst Apr. 1, 1941 Green Aug. 12, 1941 Hansen Sept. 2, 1941 Green July 6, 1943 FOREIGN PATENTS Country Date Great Britain Sept. 8, 1936 

